“You’d never catch me lighting the tank like he did. Brave man or idiot?”
There’s no air in the tank so lighting escaping propane won’t go back into the tank.
I think they started a flame at the tank before shooting it because prior experience showed that shooting a tank will not cause escaping propane to ignite on its own.
The tank didn’t blow up. The gun punched a hole or two in the tank, liquid and/or gaseous propane spewed out and ignited with a big flame.
I have shot little propane bottles before with .44 mag and they did not light, I am pretty sure there had to be some kind of flame present.